Cutter teeth for well drills



Sept l; '1942- 1.-. E. GARFIELD 2,294,544

CUTTER TEETH FOR WELL DRILLS Filed Aug. l5, 1940 2 Sheets-Sheet -1 Fig2. I

A 11|' l I 'i *u z F1315 Len/JE Garfield INVENTOR ATTORNEY l Q/ lss "lllEff-j Sept. 1, 1942. L. E. GARFIELD 2,294,544

GUTTER TEETH FOR WELL DRILLs Filed Aug. 15, 1940 2 Sheets-Sheet 2 LewisE rfzed INVENTOR ATTORNEY y Patentetl Sept. l, 1942 CUTTER TEETH FORWELL DRILLS Lewis E. Gar'eld, `Houston, Tex., assignor to Hughes ToolCompany, Houston, Tex.,a corporation of Delaware Application August 15,1940, Serial No. 352,713

(Cl. Z55-71) 1 Claim.

My invention relates to well drills of the roller cutter type employedin drilling deep wells, and particularly in hard formation.

The invention is concerned particularly with the formation of the teethupon the cutters and the manner in which the teeth are hard faced toavoid wear.

In some formations the corresponding rows of teeth upon two or morecutters tend to fall into the same track upon bottom and thus give awabbling action to the drill upon the bottom. This, as will be laterdescribed, tends to wear the adjacent sides of the rows of teeth uponthe cutters.

It is an object of the invention to soy form the teeth that the saidteeth will not wear excessively on the sides of the rows when the drillis in the ofi-center position which it tends to take.

The invention will be better understood by reference to the drawingsherewith wherein Fig. 1 is a central vertical section through the lowerend of a drill bit showing cutters mounted thereon and cutting thebottom of the hole in a normal manner.

Fig. 2 is a perspective view of a cutter toothY such as is employed uponthe Fig. 1 embodiment.

Fig. 3 is a broken transverse longitudinal section through one of theteeth of the cutters taken approximately on the line 3-3 of Fig. 1.

Fig. 4 is a perspective view of a worm cutter tooth.

Fig. 5 is a longitudinal sectional view similar to Fig. 1 and showingthe manner in which the teeth upon the cutters of a two-cone bit areconstrained to track in the same grooves cut by the adjacent cutter.

Fig. 6 is view similar to Fig. 5 but showing the cutter moved in adirection the opposite to that shown in Fig. 5.

The cutters for which my invention is particularly adapted areapproximately conical shaped cutters I, mounted upon the shafts 2 of thedrill head 3. These cutters surround the ends of the shafts 2 and arerotatable on said shafts as the cutters roll upon the bottom of thehole. Antifriction rows of rollers 4 and balls 5 assist the cutter inits free rotation upon the shaft. The rows of balls 5 act to retain thecutters upon the shafts, said balls being introduced through openings 6after. the cutters are mounted upon the shaft and a plug 'l is insertedin each of these openings to hold the balls in the raceway, said plugbeing welded at 8 to secure it in position.

Each cutter has a row of teeth 9 adjacent the 'of teeth on the adjacentcutter, so that as the cutters rotate the rows ofteeth on one will tendto engage between the rows of teeth on the adjacent cutter. Thisoisetting of the rows of teeth on one cone relative to those on theother causes the teeth shown in- Fig. 1 to cut grooves II on the bottom,while the teeth I0' on the adjacent cutter will cut grooves II on thebottom. Between these grooves cut by the two cutters are ridges ofmaterial shown at I2, which are untouched by the teeth but which breakoff in the cutting of the bottom of the hole.

When the cutter rotates in the manner shown in Fig. 1 the cuttersdescribe circles about an axis I3 indicated by the dotted line. However,when certain formations are encountered by the bit, and particularlycertain tough shale or rubbery formations, the rows of teeth on onecutter tend to track in the grooves cut by the teeth on the adjacentcutter. In order to do this the axis of rotation of the drill iseccentric to the original axis, as shown at I4 in Fig. 5. 'I'his axis,however, is a gyratory or wabbling axis which moves in a circle aboutthe axis I3 of the bit in its normal rotation. By moving this axis toone side and giving a gyratory motion to the bit the rows of teeth onone cutter may engage in the same grooves as the rows of teeth on theother, as illustrated in Fig. 5. When this is done, ridges of uncutbottom, indicated at I5, grow up on the bottom of the hole, tending toslow down the progress of the bit.

With reference to Fig. 5, it will be seen that the rows of teeth on thecutter A are crowded to a position slightly outside of their normalposition so that the heel teeth on cutter A cut the side wall of thehole and the inner sides of the rows of teeth on the cutter A will beworn away. The dotted line I6 in this view shows the originalsize of thetooth, the ends of the teeth in each row being worn away on their innersides. The result of this action of the'drill is to produce a holeoversized relative to that of the drill size.

In the cutter B the reverse is true. 'This cutter is also pushed totheleft so that the outer.

side is worn away by the ridges I5, as indicated by the dotted lines Ilon the cutter. I

In Fig. 6 the drill bit has been forced by the action of the formationto the opposite side and it will be noted that when this is done theaxis I4 upon which the cutter rotates is moved tooneside of the axis ofthe hole I3. In thisposition' diameter, which is oversize relative tothe diamv eter of the bit employed, is formed,

Thus the teeth on one cutter will wear on the inner side while the teethon the adjacent cutter will wear on the outer side, andv the teeth aregradually made narrower until, after some'period of drilling, they cometo a point -along the crest which ordinarily would have an optimumwidth, as shown in Figs. 1 and 3. The shape of the tooth when thus wornis indicated generally in Fig. 4 where the worn tooth I0 isapproximately pyramidal in form while it was originally the formindicated by the dotted lines I'I.

As there is a tendency of the bit to again rotate on a normal axisconcentric to the hole when the drill has cut through the rubberyformation whichv tends to cause it to rotate in a gyratory manner, itwill then cut the hole in a normal manner, and, if the teeth have .notbeen unduly worn in goingthrough the rubbery formation,

the drill will again rotate concentrically in thel hole. If, however,the teeth have been unduly worn as described, the drill will continue tooperate in a gyratory manner regardless ofthe formation and the ridgesI5 on bottom will strongly impede the progress of the drill.

'I'his difilculty in drilling with well drills of this character is onewhich has existed for some time and has been a source of trouble formany years. I overcome this diiliculty to a large extent by placingvhard facing'niaterial upon bothv sides of the teeth vin the rows. Theteeth are normally formed lwith a cutting vcrest 20 thereonapproximately the full width of the teeth vin the row.

The sides of the teeth aty the ends of Vthe crestl I cover with alayerof granules of hardfmaterial, such as tungsten carbide. Thesev layers 2lare o! lappreciable thickness and resist any'tendency oi the ridges I5on the bottom ofthe hole to :wear the sides of the teeth in the adjacentrows'.vr Thus when-the cutters tend to move toone side of the normalaxis of rotation of the drill and wear the sides of the rows of teeth,the teeth wilinot be quickly worn but lwill withstand the wear due to'the gyratory motion of the bit; and, when the particularly rubberyformation has been passed through, the drill will again assumel itsposition concentrically in the hole, as vshown in Fig. 1,'

and, as the teeth on the cutters have not been,

wornk on the sides covered by the hard facing 'material the drill mayagain function in the normal manner without wabbling or gyratory action.

\ 'I'he ridges I5 which tend to grow on the bottom will be broken awayand the progress of the bit will be unimpeded by said ridges. As theends of the teeth do not become materially worn when hard faced, thecrests of the teeth maintain their .length and the speed of drilling isthus not slowed down.

The hard facing material may be placed at the sides of the teeth in therow by any desirable method. Normally it may be deposited by a weldingtorch or by the electric arc by the use of a welding rod, but the mannerin which the hard facing is applied is not a material feature of theinvention.

What I claim is:

In a well dri1l, a plurality of cutters mounted to rotate thereon, andcircumferential rows of chisel shaped teeth on said cutters, crests onsaid teeth extending longitudinally of the cutter, the rows of teeth oneach cutter mounted to cut a separate track on the well bottom, saidteeth being formed with relatively more abrasion resistant material onthe outward and inward sides thereof.

' LEWIS E. GARFIELD.

